O-2, 4, 5-trichlorophenyl o, o-dialkylthiophosphates



Patented June 3, 1952 Y dNil rsro PATENT oFric-s OZ,4;S'-TRICHEGROPHENYL"OD-DIAIJKYLF THIOPHOSPHATES i Clarence L.lllloyle, Clare, Micha, assignor to The-- Dow Chemical Company,'Midland; Mich, a corporation of Delaware No Drawing. Application-March30. 1950; I Serial No. 1521976 1 This invention is directed to theO-2,4,5trichlorophenyl 0,0edialkylthiophosphates having the formula W OA31 wherein R, represents a methyl or ethyl radical. These-new compoundsare oily liquids, somewhat soluble in many organic solvents, andsubstantially insoluble in water. They are of value as toxicconstituents "of insecticide compositions.

The new compounds may be prepared by reacting O 42,4,5 trichlo'rophenyl)dichloro'thio phosphate of the formula c1-( -o- 1 t1 with an alkalimetal methylate or an alkali metal ethylate. The reaction is carried outin an inert organic solvent and conveniently in the alcohol employed inthe preparation of the alcoholate. Good results are obtained whenemploying two molecular proportions of the alcoholate with eachmolecular proportion of O-(2,4,5 trichlorophenyl)dichlorothiophosphate.In practice, the alcoholate employed is preferably the sodium salt andmay be prepared by reacting the desired alcohol with sodium in an inertorganic solvent and conveniently in an excess of the correspondingalcohol. The reaction between the alcoholate and O-(2,4,5trichlorophenyl) dichlorothiophosphate may be accomplished by addingeither reactant portionwise to the other dispersed in the reactionsolvent.

The above operations are carried out with agitation and at a temperatureof from 10 to 85 C. The reaction is somewhat exothermic, and temperaturecontrol ismaintained by regulation of the rate of addition of thereactants, as well as by the addition and subtraction of heat, ifrequired.

Upon completion of the reaction, the solvent is removed from the crudemixture by evaporation and the residue dispersed in a nonreactiveorganic solvent such as methylene dichloride, carbon tetrachloride, ordiethyl ether. The resultant mixture may be successively Washed withdilute aqueous sodium hydroxide and water, and k L2. evaporation of thesolvent. if desired,the;p13od-; uot may be further: purified' byfractional dise. tillationunder-reducedpressure.

The 0 42,4,5 trichlorophenyl)diohlorothim phosphate employed as astarting-material may be prepared. by: reacting a molecular excess-ofthiODhQSDhQryl :ch'loride- (B8613); with an alkali metal2.4-,5-trichlorophenate.. Good results are obtained when "employing from2-tQE4fmQ1eSff9 f thiophosphoryl chloride per mole of 2 j4,5'-tll'-chlorophenate. The; phenate, preferablyasz' the sodium salt,,is addedportion-wise with stirring to :the thiophosphoryl chloride 7 and thernixture subsequently warmed for a short time .to com--v pletethe-reaction. The crude reaction mixture is-then filtered and thefiltrate iractionally dis-4 tilled under reduced, pressure to separatethe product. 1

I S O-CHa I O-GHs Cl 3.43 grams (0.15 mole) of sodium was dissolved in59.7 grams (1.86 mole) of methanol to prepare an alcoholic solution ofthe corresponding alcoholate. This solution was added portionwise over aperiod of 5 minutes with stirring to 23.1 grams (0.07 mole) ofO'-(2,4,5-trichlorophenyl)- dichlorothiophosphate (having a density of1.65 at 25 C.. and a refractive index 11 of 1.6054 at 35 C.) dissolvedin 25 milliliters of methanol. The temperature rose to 40 C. during theaddition, and the mixture was subsequently maintained at the sametemperature for 10 minutes to complete the reaction. The methanol wasthen removed by evaporation, and the residue dispersed in milliliters ofdiethyl ether. The resulting dispersion was successively washed withdilute sodium hydroxide and water, and dried with anhydrous sodiumsulfate. The diethyl ether was then removed by evaporation to obtainO-2,4,5 trichlorophenyl 0,0-dimethylthiophosphate as a colorless oil.The latter product was fractionally distilled under reduced pressure toobtain substantially pure O-2,4,5-trichlorophenyl0,0-dimethylthiophosphate having a boiling point of 152+154 C., adensity of 1.46 at 28 C., and a refractive index a of 1.5597 at 35 C.

3 EXAMPLE 2 -2,4,5-trichlorophenyl 0,0-diethylthiophosphate o1fi/O-CHrCHr c1 OP o-crrz-cni 3.43 grams (0.15 mole) of sodium wasdissolved in 59 grams (1.28 mole) of ethanol and the resulting solutionadded portionwise over a period of 5 minutes with stirring to 23.1 grams(0.07 mole) of O-2,4,5-trichlorophenyl dichlorothiophosphate dissolvedin 25 milliliters of ethanol. During the addition the temperature of thereaction mixture rose to 40 C., and the mixture was subsequentlymaintained at this same temperature for minutes to complete thereaction. The ethanol was then removed from the crude reaction mixtureby evaporation, and the residue dispersed in 100 milliliters of diethylether. The resulting mixture was successively washed with dilute aqueoussodium hydroxide and water, and dried with anhydrous sodium sulfate. Thediethyl ether was then removed by evaporation to obtainO-2,4,5-trichlorophenyl 0,0-diethylthiophosphate as a pale yellow oilhaving a density of 1.32 at 23 C. and a refractive index 11 of 1.5388

at 35 C.

The new thiophosphates have been found effective as insecticides and areadapted to be employed for the control of a wide range of agriculturaland household pests. For such use the products may be dispersed on afinely divided solid and employed as dusts. Also, such mixtures may bedispersed in water with the aid of a wet-- ting agent and the resultingaqueous suspensions employed as sprays. In other procedures, theproducts may be employed in oils, as constituents of oil in wateremulsions, or in water dispersions wherein R represents a member of thegroup con-. sisting of the methyl and ethyl radicals.

2. O-2,4,5-trichlorophenyl 0,0-dimethylthiophosphate.

3. O 2,4,5 trichlorophenyl 0,0diethylthiophosphate.

CLARENCE L. MOYLE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,508,335 Moyle et a1 May 16,1950 2,520,393 Fletcher Aug. 29, 1950 FOREIGN PATENTS Number CountryDate 326,137 Great Britain Feb. 28, 1930 333,561 Great Britain Aug. 11,1930

1. AN O-2,4,5-TRICHLOROPHENYL O,O-DIALKYLTHIOPHOSPHATE HAVING THEFORMULA